Paper insulation for electric cables and the like



cs. ZAPF 1,771,946

PAPER INSULATION FOR ELECTRIC CABLES AND THE LIKE July 29, 1930.

Filed April 29. 1926 Patented July 29, 1930 UNITED STATES PATENT OFFICE GEORG ZAPI, OF COLOGNE-MULHEIM, GERMANY Application filed April 29, 1926. SerialNo.105,538, and in Germany May 8. 1925.

In insulating layers containing paper, which are subjected to fields which are not homogeneous, for instance fields having a radial direction (such as in the case of hightension cables, junction boxes, cable joints), it is desirable to build up the insulation by means of layers of different dielectric constant, the layers having the highest dielectric constant lying directly next to the conductor and the layers having a smaller dielectric constantlying further away therefrom for the purpose of'obtaining a uniform drop lation is treated with impregnating material having ditferent dielectric constants, the impregnation material having a dielectric constant which is as high as possible being used for the impregnation of the pressed layer of paper which lies immediately next to the conductor, and impregnating material the dielectric constant of which gradually decreases, being used for the subsequent layers. As the absorbing capacity of the paper is often increased by pressing, this method is especially advantageous. Now the greater the voltage the more desirable to effect this gradation of the dielectric con stant. Therefore, according to the invention use may be made of two means for the gradation by using papers pressed to different degrees, the paper that has been pressed to the greatest degree being used directly next to the conductor and being impregnated with a substance which has the highest possible dielectric constant, while the plaper layers that lie towards the outside of t e conductor are gradually graded with respect to pressure and impregnation. The paper is for instance loaded with solutions 0 organic substances such as bakeli-te or other phenol resins which are not soluble in the usual impregnating sub stances. Accordin as to whether the corresponding paper ies nearer to or further away from the conductor the solution is made stronger or weaker. After the solution is evaporated and the bakelite is converted by heat into the insoluble form the paper thus treated is used for providing the layers of insulation and is then impregnated with the usual insulating substance.

The invention may be applied to high tension cables, junction boxes and cable-joints.

The accompanying drawing shows a cross section of a high tension cable, the insulating layers of which are formed according to the present invention. a is an electric conductor composed of 37 ordinary round wires. Z) is the paper insulation showing the paper layers gradually graded, and c is a protective sheathing. 1

lVhat I claim is A paper insulation for an electric conductor comprising layers of paper pressed to different degrees and impregnated with material having different dielectric constants, the layers of paper lying directly next to the conductor being pressed to the greatest extent and being impregnated with the material having the greatest dielectric constant so that the dielectric constant of the insulation gradually decreases as the distance from the con ductor increases.

In testimony whereof I have signed my name to this specification.

GEORG ZAPF. 

